FreeBSD_HEAD_i386 - Build #1321 - Fixed

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FreeBSD_HEAD_i386 - Build #1321 - Fixed:

Build information: https://jenkins.FreeBSD.org/job/FreeBSD_HEAD_i386/1321/
Full change log: https://jenkins.FreeBSD.org/job/FreeBSD_HEAD_i386/1321/changes
Full build log: https://jenkins.FreeBSD.org/job/FreeBSD_HEAD_i386/1321/console

Change summaries:

288948 by gjb:
Update the last check revision marker.

Sponsored by:	The FreeBSD Foundation

288947 by gjb:
Document r288943, clang, llvm, etc. updated to upstream 3.7.0.

Sponsored by:	The FreeBSD Foundation

288944 by cem:
Fix core corruption caused by race in note_procstat_vmmap

This fix is spiritually similar to r287442 and was discovered thanks to
the KASSERT added in that revision.

NT_PROCSTAT_VMMAP output length, when packing kinfo structs, is tied to
the length of filenames corresponding to vnodes in the process' vm map
via vn_fullpath.  As vnodes may move during coredump, this is racy.

We do not remove the race, only prevent it from causing coredump
corruption.

- Add a sysctl, kern.coredump_pack_vmmapinfo, to allow users to disable
  kinfo packing for PROCSTAT_VMMAP notes.  This avoids VMMAP corruption
  and truncation, even if names change, at the cost of up to PATH_MAX
  bytes per mapped object.  The new sysctl is documented in core.5.

- Fix note_procstat_vmmap to self-limit in the second pass.  This
  addresses corruption, at the cost of sometimes producing a truncated
  result.

- Fix PROCSTAT_VMMAP consumers libutil (and libprocstat, via copy-paste)
  to grok the new zero padding.

Reported by:	pho (https://people.freebsd.org/~pho/stress/log/datamove4-2.txt)
Relnotes:	yes
Sponsored by:	EMC / Isilon Storage Division
Differential Revision:	https://reviews.freebsd.org/D3824

288943 by dim:
Upgrade our copies of clang, llvm, lldb, compiler-rt and libc++ to 3.7.0
release.

Please note that from 3.5.0 onwards, clang, llvm and lldb require C++11
support to build; see UPDATING for more information.

Release notes for llvm and clang can be found here:
<http://llvm.org/releases/3.7.0/docs/ReleaseNotes.html>
<http://llvm.org/releases/3.7.0/tools/clang/docs/ReleaseNotes.html>

Thanks to Ed Maste, Andrew Turner and Antoine Brodin for their help.

Exp-run:	antoine
Relnotes:	yes

288937 by gjb:
Document r288669, stack protector "strong" level.

Help from:	pfg
Sponsored by:	The FreeBSD Foundation

288936 by gjb:
Document r288654, lagg(4) fec removal.

Sponsored by:	The FreeBSD Foundation

288934 by ngie:
Add directory for test encoder missed by accident in r288929

Sponsored by: EMC / Isilon Storage Division

288933 by ngie:
Remove a comment from an earlier iteration of trying to figure out how the
test encoder testcases worked